01 - Line a baking sheet with parchment paper and set aside.
02 - Place the chopped dark chocolate in a heatproof bowl and melt using a double boiler method over a saucepan of simmering water, or microwave in 20-second bursts, stirring between intervals until completely smooth.
03 - Fold the chopped walnuts, toasted coconut, and crisp rice cereal into the melted chocolate, stirring until all ingredients are evenly coated.
04 - If desired, stir in maple syrup or honey for extra sweetness and mix until well incorporated.
05 - Drop tablespoon-sized mounds of the mixture onto the prepared baking sheet, spacing them slightly apart to prevent sticking.
06 - Sprinkle the tops of each cluster with flaky sea salt if desired for a sweet-salty contrast.
07 - Refrigerate the clusters for at least 30 minutes, or until the chocolate is fully set and firm to the touch.
08 - Transfer the set clusters to an airtight container and store in the refrigerator for up to 1 week.